fix: rename deps/Cmakelists.txt → CMakeLists.txt (case-sensitive Linux fix)

macOS filesystem is case-insensitive so both spellings worked locally,
but the Linux container (CI) could not find the file and failed with
"does not contain a CMakeLists.txt file".

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

code/deps/CMakeLists.txt

@@ -0,0 +1,56 @@
+# deps/CMakeLists.txt
+#
+# Lazy tarball extraction – a dependency is only extracted when its directory
+# does not yet exist.  Extraction happens at cmake configure time.
+#
+# Which deps are extracted depends on the active build mode:
+#
+#   (default)      Eigen only          → tests-only build
+#   WITH_VIEWER=ON + Eigen, libigl, libigl-glad, glfw
+#   WITH_CGAL=ON   + Eigen, CGAL       (WITH_VIEWER is implied by WITH_CGAL)
+#
+
+function(setup_dependency NAME SUBDIR)
+    if(NOT EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/${NAME}")
+        file(MAKE_DIRECTORY "${NAME}")
+        file(GLOB TARBALL "${CMAKE_CURRENT_SOURCE_DIR}/tarballs/${NAME}.tar.*")
+        message(STATUS "${CMAKE_CURRENT_SOURCE_DIR}")
+        if(NOT TARBALL)
+            message(FATAL_ERROR "❌ No '${NAME}*.tar.*' in deps/tarballs/")
+        else()
+            message(STATUS "${CMAKE_COMMAND}  ${TARBALL}")
+            if(SUBDIR STREQUAL "")
+                execute_process(
+                    COMMAND "${CMAKE_COMMAND}" -E tar xf "${TARBALL}"
+                    RESULT_VARIABLE TAR_STATUS
+                    WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}")
+            else()
+                execute_process(
+                    COMMAND "${CMAKE_COMMAND}" -E tar xf "${TARBALL}" "${NAME}/${SUBDIR}"
+                    RESULT_VARIABLE TAR_STATUS
+                    WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}")
+            endif()
+            message(STATUS "Extracting ${NAME}... Status: ${TAR_STATUS}")
+            if(NOT TAR_STATUS EQUAL 0)
+                message(FATAL_ERROR "❌ Extract failed: ${NAME}")
+            endif()
+        endif()
+    else()
+        message(STATUS "✅ ${NAME} already exists, skipping extraction.")
+    endif()
+endfunction()
+
+# ── Always required ────────────────────────────────────────────────────────────
+setup_dependency("eigen-3.4.0" "Eigen")
+
+# ── Viewer mode ────────────────────────────────────────────────────────────────
+if(WITH_VIEWER)
+    setup_dependency("libigl-2.6.0"  "include")
+    setup_dependency("libigl-glad"   "")
+    setup_dependency("glfw-3.4"      "")
+endif()
+
+# ── CGAL mode ─────────────────────────────────────────────────────────────────
+if(WITH_CGAL)
+    setup_dependency("CGAL-6.1.1" "include")
+endif()